Oxygen transport membrane (OTM) based reforming systems can be used for conversion of hydrocarbons to syngas product much like conventional steam methane reformer (SMR), partial oxidation (PDX) reactor, and autothermal reactor (ATR). However, in contrast to the conventional processes, OTM-based reforming systems' operation and process control can be substantially different. In an SMR plant, heat required for endothermic reforming reactions is provided by burning fuel outside of the reformer tubes, and/or by heat transfer from a hot gas stream which can be controlled independently from reformer fuel and steam process feed flow. In PDX and ATR plants, the fraction of process feed combusted to support the thermal demand in the reactor depends on the flowrate of oxygen provided to the reactor which can be controlled independently from process fuel and steam feed flow. However, in an OTM-based reforming system employing thermally-coupled reforming reactors and OTM reactors, the heat required for endothermic reforming reactions occurring inside the reforming reactors is provided by the exothermic oxidation reactions occurring inside the OTM reactors. The amount of heat released depends on the oxygen flux achieved through the action of the oxygen transport membranes. Unlike the PDX and ATR where gaseous oxygen is supplied as a separate feed, there is no direct flow control of oxygen input in OTM reactor. The oxygen input in OTM reactor will be governed by the properties of the oxygen transport membrane, operating temperature of the OTM reactor, and oxygen partial pressure gradient across the oxygen transport membrane. Thus, the OTM reactors in the OTM-based reforming system can produce excess heat causing the OTM reactor surface temperature to rise beyond a target maximum operating temperature, or can produce less than adequate heat to support endothermic reactions occurring in the reforming reactors while maintaining the OTM reactor temperature within a desired range to achieve the required oxygen flux for heat generation.
The present invention therefore, provides a method for thermally-stabilizing an oxygen transport membrane based reforming system through modulation of the flow rate of hydrocarbon-containing feed to the reforming reactors, steam-to-carbon ratio of the combined feed stream fed to the reforming reactors, the flow rate of cooling air, temperature and flow rate of oxygen-containing stream, or combinations thereof. The invention also relates to a method for thermally-stabilizing OTM-based reforming system through measurement and control of the syngas product oxygen-to-carbon ratio in a desired range such that the OTM-based reforming system is operated close to the thermo-neutral point.